The "market clearing price" is most closely associated with

The "market clearing price" is most closely associated with the equilibrium price. 
The equilibrium price is the market price where the quantity of goods supplied is equal to the quantity of goods demanded. 

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.